Multilayer coil component

ABSTRACT

Disclosed herein is a multilayer coil component including a copper-nickel mixture for an internal electrode, in which a nickel content in the internal electrode is adjusted to thereby optimize the area ratio of nickel to copper while the copper-nickel mixture is used for a material for the internal electrode of the multilayer coil component, thereby preventing deterioration in characteristics of the multilayer coil component, so that ferrite characteristics of the multilayer coil component, such as, impedance (Z), inductance (L), and the like, can be improved.

CROSS REFERENCE(S) TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. Section 119 ofKorean Patent Application Serial No. 10-2012-0131551, entitled“Multilayer Coil Component” filed on Nov. 20, 2012, which is herebyincorporated by reference in its entirety into this application.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a multilayer coil component.

2. Description of the Related Art

As the trend toward miniaturization, high-capacity, and high-efficiencyof electronic devices such as smart phones, computer tablets, and PCs isaccelerating, the importance of electronic components such as inductorsconstituting them is growing bigger and bigger. The reason is that, asvarious kinds of electronic devices become smaller and have highercapacitance, electronic components are integrated in a smaller space,electromagnetic interference between electronic components becomesgreater, and the number of active elements is increased due to anincrease in amount of information to be treated, resulting in anincreasing demand for passive elements.

The multilayer coil component including the inductor has been used inmany different fields since it has no leakage magnetic flux because ofan internal electrode covered with a magnetic material, and suppressedcross-talk; is suitable for high-density assembly and miniaturizablewhile retaining inductance (L); and maintains high reliability.

This multilayer coil component is usually manufactured by laminating andintegrating magnetic sheets or sheets on which a magnetic paste and apaste for internal electrodes are printed by a printing method, a doctorblade method, or the like, and then printing a paste for externalelectrodes on a surface of a sintered body obtained by firing thelaminate at a high temperature and firing it.

As a material for the internal electrode layer, silver (Ag) having lowresistivity from the influence of direct current resistance of themultilayer coil component is mainly used. Silver (Ag), which is a noblemetal, is not oxidized at a high temperature, and thus, a de-binderprocess (removing organic substances from a half-finished product at ahigh temperature) and a sintering process may be employed under ageneral atmosphere. However, since, in spite of these advantages, silveris a noble metal, it is expensive and temporary price variation thereofis large. Recently, inflated prices of silver impose a heavy burden onproduct cost, and thus a material as a replacement for silver needs tobe developed.

Therefore, many studies on several metals generally useable as aninternal electrode instead of silver (Ag) have been conducted. However,since most metals except for copper (Cu) have higher resistivity thansilver, they are known to be inappropriate as an internal electrode forgeneral coil elements except for as particular purposes in which lowefficiency is ignored.

In order to solve these defects, the movement of replacing silver (Ag)with cheap copper (Cu), as a material for the internal electrode of themultilayer coil component, has been taken. However, copper hassubstantially not been used as the material for the internal electrodedue to easy oxidation thereof in spite of excellent pricecompetitiveness.

Therefore, in order to replace silver with copper as a material for theinternal electrode of the multilayer coil component, the foregoingproblems need to be urgently solved,

Meanwhile, a multilayer ceramic condenser (hereinafter, referred to asMLCC) is manufactured by printing a conductive paste on moldeddielectric sheets through screen, gravure, or other methods, to therebyform internal electrode layers, and then laminating the sheets havinginternal electrode layers printed thereon. The internal electrode layersof the MLCC have been known to be formed by using a metal powder mainlysuch as nickel (Ni), copper (Cu), or the like.

There are many similarities between the MLCC and the multilayer coilcomponent in view of an external shape and a manufacturing method.However, the MLCC is a product where thin square shaped internalelectrodes formed on dielectric ceramic sheets are alternately laminatedto implement high capacitance, and is a parallel type condenser wherethe respective internal electrodes are not contacted with each otherinside a chip.

Meanwhile, in the case of the multilayer coil component, coil typeinternal electrodes are formed on a ceramic inner layer and the coiltype internal electrodes are connected with each other to implementinductance and impedance of a circuit with respect to current flowingthrough the coil.

In addition, the MLCC is mainly fired at a high temperature of 1000° C.or higher, and thus has a different mechanism from the multilayer coilcomponent fired at a temperature below 1000° C.

In addition, in the case of the multilayer coil component, theresistance of the internal electrode is increase when the internalelectrode is formed of copper, and thus the use of copper is restricted.However, in the case of the MLCC, there is no problem with theresistance (Rdc), and even though the internal electrode is oxidized dueto the use of copper as the internal electrode, the application thereofis believed not to be too much trouble.

Therefore, even though copper and nickel are generally used as amaterial for an internal electrode layer of the existing MLCC, the usethereof as a material for the internal electrode of the multilayer coilcomponent by simple replacement from this technology is still limited.

RELATED ART DOCUMENT Patent Document

(Patent Document 1) US Patent Laid-Open Publication No. 2011-0285494

SUMMARY OF THE INVENTION

An object of the present invention is to provide a multilayer coilcomponent capable of solving problems of the related art, caused byusing copper instead of silver as a material for an internal electrodeof the existing multilayer coil component.

According to an exemplary embodiment of the present invention, there isprovided a multilayer coil component including: a main body having aplurality of ceramic layers therein; and a plurality of internalelectrodes formed on the plurality of ceramic layers, respectively, theinternal electrodes being interlayer-connected to each other through viaholes of the ceramic layers to form a coil pattern, wherein the internalelectrode contains a copper-nickel mixture.

The copper-nickel mixture may be at least one selected from the groupconsisting of a copper-nickel mixed powder, a copper-nickel alloy, and acopper powder coated with nickel.

Here, a nickel content in the internal electrode may be 5˜25 wt %.

The ceramic layer may be formed of NiZn ferrite or MnNiZn ferrite.

According to another exemplary embodiment of the present invention,there is provided a multilayer coil component including: a main bodyhaving a plurality of ceramic layers therein; and a plurality ofinternal electrodes formed on the plurality of ceramic layers,respectively, the internal electrodes being interlayer-connected to eachother through via holes of the ceramic layers to form a coil pattern,wherein the internal electrode contains a copper-nickel mixture, andwherein a nickel content in the internal electrode satisfies 5≦Ni(wt%)≦25.

The copper-nickel mixture may be at least one selected from the groupconsisting of a copper-nickel mixed powder, a copper-nickel alloy, and acopper powder coated with nickel.

The ceramic layer may be formed of NiZn ferrite or MnNiZn ferrite.

According to still another exemplary embodiment of the presentinvention, there is provided a multilayer coil component including: amain body having a plurality of ceramic layers therein; and a pluralityof internal electrodes formed on the plurality of ceramic layers,respectively, the internal electrodes being interlayer-connected to eachother through via holes of the ceramic layers to form a coil pattern,wherein the internal electrode contains a copper-nickel mixture, andwherein a nickel and ferrite mixed region is formed at an interfacebetween the internal electrode and the ceramic layer.

The nickel and ferrite mixed region may be formed by containing nickelof the internal electrode and ferrite of the ceramic layer.

The nickel and ferrite mixed region may have a thickness of 0.2˜5 μm.

Here, a nickel content in the internal electrode may be 5˜25 wt %.

The copper-nickel mixture may be at least one selected from the groupconsisting of a copper-nickel mixed powder, a copper-nickel alloy, and acopper powder coated with nickel.

The ceramic layer may be formed of NiZn ferrite or MnNiZn ferrite.

The multilayer coil component may be a multilayer chip inductor, amultilayer chip bead, or a multilayer power inductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional structure of a multilayer coil componentaccording to an exemplary embodiment of the present invention;

FIG. 2 shows a cross-sectional structure of a multilayer coil componentaccording to another exemplary embodiment of the present invention;

FIG. 3 shows a structure in which a nickel and ferrite mixed region isformed at an interface between an internal electrode and a ceramic layerin FIG. 2;

FIG. 4 shows an inner structure of the internal electrode in FIG. 2;

FIG. 5 shows a coil forming procedure in manufacturing the multilayercoil component according to the exemplary embodiment of the presentinvention;

FIGS. 6 and 7 show impedance measurement results of multilayer coilcomponents manufactured according to Example and Comparative Example,respectively;

FIG. 8 is an optical microscope image of a cross-sectional structure ofthe multilayer coil component according to the exemplary embodiment ofthe present invention;

FIG. 9 is a scanning electron microscope image of a part of the opticalmicroscope image of FIG. 8; and

FIGS. 10A and 10B are images showing distributions of copper (a) andnickel (b) in an internal electrode, which are measured by EPDA mappingof FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

Terms used in the present specification are for explaining the exemplaryembodiments rather than limiting the present invention. As used herein,unless explicitly described to the contrary, a singular form includes aplural form in the present specification. Also, used herein, the word“comprise” and/or “comprising” will be understood to imply the inclusionof stated constituents, steps, operations and/or elements but not theexclusion of any other constituents, steps, operations and/or elements.

The present invention is directed to a multilayer coil component capableof using cheap copper as a replacement for a material for an internalelectrode.

A multilayer coil component according to an exemplary embodiment of thepresent invention, referring to FIG. 1 showing a cross section thereof,may include: a main body 110 having a plurality of ceramic layerstherein; and a plurality of internal electrodes 120 formed on theplurality of ceramic layers, respectively, the internal electrodes 120being interlayer-connected to each other through via holes of theceramic layers to form a coil pattern, wherein the internal electrode120 contains a copper-nickel mixture.

In the case where only copper is used as a material for the internalelectrode like the related art, resistance of the internal electrode maybe increased due to oxidation of copper in a plasticizing process,resulting in deteriorating characteristics of the multilayer coilcomponent. In the present invention, copper and nickel may be used bymixture to prevent the foregoing defect.

In addition, when copper and nickel are used by mixture as the materialfor the internal electrode, this interrupts contact between the ceramiclayer and the internal electrode, and thus increases insulationresistance, which may be generated between two materials, so that thedeterioration in characteristics of the multilayer coil component can beprevented.

The copper-nickel mixture according to the present invention may containat least one selected from the group consisting of a copper-nickel mixedpowder, a copper-nickel alloy, and a copper powder coated with nickel.

The copper-nickel mixed powder mean one in which a copper powder and anickel powder are simply mixed. Here, the nickel content in thecopper-nickel mixed powder may be preferably 5˜25 wt % based on thetotal content of the copper-nickel mixed powder. If the nickel contentin the copper-nickel mixed powder is below 5 wt %, the effect ofsuppressing reaction between copper and a magnetic material isinsufficient and thus oxidation of copper may be still insufficientlyprevented. If above 25 wt %, the resistance (Rdc) is too high, resultingin deteriorating characteristics of the multilayer coil component.

In addition, the copper-nickel alloy means one in which copper andnickel are an alloy type. A method of preparing the copper-nickel alloyis not particularly limited. Copper and nickel may be alloyed by using aknown method, and a commercial copper-nickel alloy may be used. Thenickel content in the copper-nickel alloy may be preferably 5˜25 wt %.If the nickel content in the copper-nickel alloy is below 5 wt %, theeffect of suppressing reaction between copper and a magnetic material isinsufficient and thus oxidation of copper may be still insufficientlyprevented. If above 25 wt %, the resistance (Rdc) is too high, resultingin deteriorating characteristics of the multilayer coil component.

In addition, the copper powder coated with nickel means that a surfaceof a copper powder is coated with nickel. A nickel layer coated on thecopper powder has a thickness of preferably 0.2˜1.0 μm, but is notparticularly limited thereto. However, the content of nickel coated onthe copper powder may be preferably 5˜25 wt % based on the total contentthereof. If the nickel content in the copper powder coated with nickelis below 5 wt %, the effect of suppressing reaction between copper and amagnetic material is insufficient and thus oxidation of copper may bestill insufficiently prevented. If above 25 wt %, the resistance (Rdc)is too high, resulting in deteriorating characteristics of themultilayer coil component.

As the ceramic layer of the present invention, soft magnetic ferrite maybe applied, and in particular, NiZn ferrite or MnNiZn ferrite may bepreferably used. Here, the ceramic layer may further contain glass,Bi₂O₂, V₂O₅, or the like, as a sintering aid, but is not limitedthereto.

In addition, in order to form the ceramic layer, known solvent andpolymer binder may be further contained therein, but the kinds andcontents thereof are not particularly limited, and are appropriate forforming a general ceramic layer.

In addition, the multilayer coil component includes external electrodes130. The external electrodes 130 may be formed of the same material asthe internal electrode 120 or other metals, but the material therefor isnot particularly limited.

The multilayer coil component having the foregoing structure may beapplied to all of a bead type, a general inductor type, and a powerinductor type.

In addition, a multilayer coil component according to another exemplaryembodiment of the present invention, referring to FIG. 1 showing a crosssection thereof, may include: a main body 110 having a plurality ofceramic layers therein; and a plurality of internal electrodes 120formed on the plurality of ceramic layers, respectively, the internalelectrodes 120 being interlayer-connected to each other through viaholes of the ceramic layers to form a coil pattern, wherein the internalelectrode 120 contains a copper-nickel mixture, and wherein a nickelcontent in the internal electrode satisfies 5≦Ni(wt %)≦25.

According to the above exemplary embodiment, the copper-nickel mixtureis used for the internal electrode and the nickel content in thecopper-nickel mixture is 5˜25 wt % based on the entire internalelectrode, thereby maximizing characteristics of the multilayer coilcomponent of the present invention.

The copper-nickel mixture according to the present invention may containat least one selected from the group consisting of a copper-nickel mixedpowder, a copper-nickel alloy, and a copper powder coated with nickel.The copper-nickel mixed powder, the copper-nickel alloy, and the copperpowder coated with nickel, which are copper-nickel mixtures used in thepresent invention, have the same meanings as described in the foregoingexemplary embodiment.

If the nickel content in the copper-nickel mixture is below 5 wt %, theeffect of increasing insulation resistance between copper and ferrite ofthe ceramic layer is insufficient. If above 25 wt %, the resistance(Rdc) is too high, resulting in deteriorating characteristics of themultilayer coil component.

As the copper-nickel mixture according to the present exemplaryembodiment, various types of copper-nickel mixtures may be used like inthe foregoing exemplary embodiment. Here, the resistance (Rdc) of themultilayer coil component may be maintained at a predetermined requestedlevel by using an internal electrode containing a nickel content of 5˜25wt %.

The ceramic layer of the present invention may be formed of preferablyNiZn ferrite or MnNiZn ferrite, and here, may further contain glass,Bi₂O₃, V₂O₅, or the like, as a sintering aid, but is not limitedthereto. In addition, in order to form the ceramic layer, known solventand polymer binder may be further contained therein, but the kinds andcontents thereof are not particularly limited, and are appropriate forforming a general ceramic layer.

In addition, the multilayer coil component includes external electrodes130. The external electrodes 130 may be formed of the same material asthe internal electrode 120 or other metals, but the material therefor isnot particularly limited.

The multilayer coil component having the foregoing structure may beapplied to all of a bead type, a general inductor type, and a powerinductor type.

In addition, a multilayer coil component according to still anotherexemplary embodiment of the present invention, referring to FIG. 2showing a cross section thereof, may include: a main body 110 having aplurality of ceramic layers therein; and a plurality of internalelectrodes 120 formed on the plurality of ceramic layers, respectively,the internal electrodes 120 being interlayer-connected to each otherthrough via holes of the ceramic layers to form a coil pattern, whereinthe internal electrode 120 contains a copper-nickel mixture, and whereina nickel and ferrite mixed region 140 is formed at an interface betweenthe internal electrode 120 and the ceramic layer.

The term “nickel and ferrite mixed region 140” means a region formed byincluding nickel contained in the internal electrode 120 and ferritecontained in the ceramic layer. The nickel and ferrite mixed regioncontains mainly nickel and partially ferrite.

The internal electrode 120 according to the present exemplary embodimentmay be formed of the copper-nickel mixture, and the nickel and ferritemixed region 140 is formed at the interface between the internalelectrode 120 and the ceramic layer while the nickel and ferrite mixedregion 140 is formed by nickel moving out from the copper-nickel mixtureused for the internal electrode 120 and ferrite moving out from theceramic layer.

Referring to FIG. 3 showing an enlarged structure of a circle partincluding the internal electrode in FIG. 2 and FIG. 4 showing astructure of the internal electrode, the internal electrode 120 formedof the copper-nickel mixture is formed inside the nickel and ferritemixed region 140.

In the internal electrode 120, the area ratio of nickel to copper(A_(Ni)/A_(Cu) ratio) may be preferably in a range of 0.03˜0.2. If thearea ratio of nickel to copper is below 0.03 in the internal electrodeand the nickel content is too little, the effect of suppressingoxidation of copper is insufficient. If above 0.2 and thus the nickelcontent is too much, the resistance (Rdc) is too high, resulting indeteriorating characteristics of the multilayer coil component.

The area ratio of nickel to copper in the internal electrode 120according to the present invention is calculated by using the area ofonly nickel present in the internal electrode 120, except for nickeldistributed within a thickness of 0˜1.0 μm from an interface between theinternal electrode 120 and the ceramic layer.

In addition, the nickel contained in the internal electrode 120 movesout from the internal electrode 120 during a firing procedure, andferrite moves out from the ceramic layer, to separately form a nickeland ferrite mixed region 140 at the interface between the internalelectrode 120 and the ceramic layer. Therefore, the area ratio of nickelto copper in the internal electrode 120 of the present invention iscalculated by using only the area of nickel present in the internalelectrode 120, itself, except for the area of nickel contained in thenickel and ferrite mixed region 140.

Specifically, any region of the internal electrode except for a regioncorresponding to a thickness of 0˜1.0 μm from the interface between theinternal electrode and the ceramic layer is selected and then an opticalmicroscope image thereof is obtained. Then, when an EPMA mappingprocedure is conducted from the optical microscope image, an image wherecopper and nickel are indicated in different colors may be obtained.From the obtained image, the ratio of area occupied by nickel to areaoccupied by copper in the total area of the internal electrode may becalculated.

In addition, referring to FIG. 3 showing an enlarged structure of theinternal electrode 120 in FIG. 2, the nickel and ferrite mixed region140 in which nickel moving out from the internal electrode 120 andferrite moving out from the ceramic layer are mixed is formed at theinterface around the internal electrode 120.

The nickel and ferrite mixed region 140 serves as a barrier suppressingreaction between copper of the internal electrode 120 and ferrite of theceramic layer, thereby effectively preventing an increase in resistancedue to oxidation of copper.

In addition, the nickel and ferrite mixed region 140 functions as a kindof insulating film, to thereby improve insulation resistance (IR) of theceramic body, and improve electric characteristics (impedance) to adesired level while minimizing resistance loss.

The nickel and ferrite mixed region 140 of the present invention has athickness of 0.2˜5 μm, which is particularly preferable in view ofimproving insulation resistance and electric characteristics.

The copper-nickel mixture used for the internal electrode 120 accordingto the exemplary embodiment of the present invention may contain atleast one selected from the group consisting of a copper-nickel mixedpowder, a copper-nickel alloy, and a copper powder coated with nickel.The copper-nickel mixed powder, the copper-nickel alloy, and the copperpowder coated with nickel, which are copper-nickel mixtures used in theexemplary embodiment of the present invention, have the same meanings asdescribed in the foregoing exemplary embodiment.

If the nickel content in the copper-nickel mixture is below 5 wt %, theeffect of suppressing reaction between copper and a magnetic material isinsufficient and thus oxidation of copper may be still insufficientlyprevented. If above 25 wt %, the resistance (Rdc) is too high, resultingin deteriorating characteristics of the multilayer coil component.

The ceramic layer of the present invention may be formed of preferablyNiZn ferrite or MnNiZn ferrite, and here, may further contain glass,Bi₂O₃, V₂O₅, or the like, as a sintering aid, but is not limitedthereto. In addition, in order to form the ceramic layer, known solventand polymer binder may be further contained therein, but the kinds andcontents thereof are not particularly limited, and are appropriate forforming a general ceramic layer.

In addition, the multilayer coil component includes external electrodes130. The external electrodes 130 may be formed of the same material asthe internal electrode 120 or other metals, but the material therefor isnot particularly limited.

The multilayer coil component having the foregoing structure may beapplied to all of a bead type, a general inductor type, and a powerinductor type.

Hereinafter, a procedure of manufacturing the multilayer coil componentaccording to the present invention will be described with reference toFIG. 5. First, the multilayer coil component is manufactured by formingvia holes 111 for interlayer interaction in ceramic layers 110containing an organic material, which are molded through tape molding,and then printing an internal electrode paste (internal electrode 120)on the sheets, fitting to the holes 20, to form patterns. When the thusprinted patterns are laminated according to the accurate positions, theinternal electrode paste is connected through via holes 111, therebyentirely forming a coil. The coil type half-finished product is cut intoseparate chips, and hot air is applied thereto under atmosphere toremove the organic material (de-binder). The resultant product is firedin a furnace at a high temperature of 800° C. or higher, thereby forminga chip inductor.

The ceramic layer is formed into a magnetic sheet (ferrite sheet) from aferrite paste containing NiZn ferrite or MnNiZn ferrite. Specifically, asolvent such as ethanol or the like and a binder such as PVA or the likeare added to and mixed with a ferrite fine powder after plasticizing andpulverizing, containing Fe₂O₃, NiO, CuO, and ZnO, as a main component,to thereby prepare a ferrite paste, and then this ferrite paste iscoated on a film such as PET or the like, in a shape of a surface, by adoctor blade method or the like, thereby obtaining the magnetic sheet(ferrite sheet).

Then, a predetermined arrangement of via holes are formed in the ceramiclayers by punching using molding, perforating using a laser process, orthe like, and then a conductive paste for forming an internal electrodeis printed on the ceramic layers to have predetermined patterns.

In addition, in the case where the multilayer coil component accordingto the present invention is a multilayer power inductor, a gap layer maybe further formed inside the ceramic layer by using a non-magneticmaterial.

In the present invention, the internal electrodes are formed on theceramic layers by using at least one selected from the group consistingof a copper-nickel mixture powder where copper and nickel are mixed witheach other, a copper-nickel alloy, and a copper powder coated withnickel. It is important to contain 5˜25 wt % of nickel in thecopper-nickel mixture used in the internal electrode according to thepresent invention. In addition, a method of forming the internalelectrode is not particularly limited, and may follow the known methodsof the related art such as a printing method or a doctor blade method.

The respective ceramic layers having the internal electrodes thereon arelaminated and integrated while the internal electrodes are connectedwith each other through vias to constitute a spiral shape of coil. Thelaminate is cut into a predetermined dimension, to obtain a chip typeunfired laminate.

The unfired laminate is subjected to a plasticizing process for removinga binder component, by being heated in the air at a temperature of about150˜400° C. In the present invention, the copper-nickel mixture is usedfor the internal electrode, to allow nickel to suppress the reactionbetween the ceramic layer and copper and thus prevent oxidation ofcopper during the plasticizing process. Therefore, the problems of therelated art, such as, the increase in resistance and the deteriorationin characteristics of the multilayer coil component due to oxidation ofcopper, can be solved. In addition, the plasticizing process of thelaminate chip can be easily carried out due to the effect of suppressingoxidation of copper.

Then, the unfired laminate after removing the binder component is fired,to obtain a chip shaped laminate. Conditions for the firing process arenot particularly limited. The firing process may be carried outaccording to the firing conditions for a general multilayer coilcomponent, and may be preferably carried out in reduced ambience whereoxygen is excluded.

In addition, in order to form external electrodes, a conductive paste iscoated on both end portions of the chip shaped laminate by a dip coatingmethod or the like. As the conductive paste for forming externalelectrodes, the same material as the internal electrode may be used or ametal paste of the related art containing silver (Ag) as a maincomponent may be used, but the kind of material is not particularlylimited.

In addition, a multilayer inductor may be manufactured by firing thelaminate and then forming external electrodes at both end portions ofthe laminate. A plating process using nickel, tin, or the like may beapplied to the external electrodes.

Hereinafter, examples of the present invention will be described indetail. The following examples merely illustrate the present invention,but the scope of the present invention should not be construed to belimited by these examples. Further, the following examples areillustrated by using specific compounds, but it is apparent to thoseskilled in the art that equivalents thereof are used to obtain equal orsimilar levels of effects.

Examples and Comparative Examples

Each of the multilayer inductors having a structure shown in FIG. 1 wasmanufactured by using a material for an internal electrode having anickel content as shown in Table 1 below and including a process offorming the internal electrode as shown in FIG. 5.

Experimental Example 1

Impedance and Rdc of each of the multilayer inductors manufactured inthe examples were measured, and the measurement results were tabulatedin Table 1 below. In addition, impedance and Rdc measurement results ofSample Nos. 1 and 9 were shown in FIGS. 6 and 7.

TABLE 1 Ni content Area ratio of nickel Sample in Internal to copper inImpedance No. Electrode (wt %) Internal Electrode (Ohm) Rdc (ohm)  1* 00 400 166  2* 3 0.015 419 170 3 5 0.030 482 178 4 7 0.033 548 183 5 100.055 625 187 6 13 0.085 666 216 7 15 0.133 670 231 8 18 0.136 668 255 920 0.152 696 265 10  23 0.174 699 266 11  25 0.200 708 297 12* 27 0.212711 311 13* 30 0.235 712 324 14* 35 0.266 710 366 *indicates a samplethat is not included in the scope of the present invention.

In addition, it may be seen from the results of Table 1 above that, atthe time of manufacturing the multilayer inductor according to thepresent invention, the resistance of the multilayer inductor can beeffectively controlled by adjusting the nickel content to 5˜25 wt %while copper and nickel are used by mixture for the internal electrode.If the nickel content in the internal electrode is below 5 wt % (SampleNos. 1 and 2), the increase in impedance and the decrease in resistanceare insufficient. If above 25 wt % and thus a large amount of nickel iscontained in the internal electrode (Sample No. 12 to 14), an increasein impedance is insignificant but Rdc is increased, resulting indeteriorating characteristics of the multilayer inductor.

In addition, the impedance (Z) of the multilayer inductor using aninternal electrode in which nickel is not added (100 wt % of copper isonly used) was measured to a level of 400 ohm (@100 MHz, Agilent 4291B,Fixture 16193A), as shown in FIG. 6.

However, the impedance (Z) of the multilayer inductor using an internalelectrode in which 20 wt % of nickel is contained was measured to about696 ohm, as shown in FIG. 7.

In addition, it may be seen that frequencies at which maximum points ofimpedance and R-X cross points are shown are similar in FIGS. 6 and 7.Impedance |Z|=R+jX, and when bead products are identical in view ofdesign (size, area, and winding number of a coil), and materialpermeability, R-X cross points thereof are also identical. In the samedesign, increased permeability moves the R-X cross point to lowerfrequency, and decreased permeability moves the R-X cross point tohigher frequency. Therefore, from the above results, it may bedetermined that permeability of the ferrite materials are the same andit may be seen that the impedance (Z) characteristics are largely varieddepending on whether or not the internal electrode contains nickel.

Experimental Example 2

A structure of the multilayer inductor manufactured according to theexemplary embodiment of the present invention was confirmed by anoptical microscope and the results were shown in FIG. 8. In addition, apart of FIG. 8 was observed by a scanning electron microscope and theresults were shown in FIG. 9. In addition, through EPMA mapping of FIG.9, morphology of copper was shown in FIG. 10A and morphology of nickelwas shown in FIG. 10B. From the results, the area ratio of nickel tocopper in the internal electrode was calculated, which was then shown inTable 1 above.

Next, referring to FIG. 8, the multilayer inductor according to thepresent invention includes ceramic layers and internal electrodesprinted on the ceramic layers, and it may be confirmed that copper(white) and nickel (black) were mixed and distributed in the internalelectrode; and a black band shape of a nickel and ferrite mixed region(3˜5 μm) was formed at the interface between the internal electrode andthe ceramic layer.

In addition, it may be seen that, also in the image of FIG. 9, which wasobtained by observing a part of FIG. 8 through a scanning electronmicroscope, nickel (black) and copper (white) were mixed and distributedin the internal electrode and a black band shape and a nickel andferrite mixed region were formed at the interface between the internalelectrode and the ceramic layer.

It may be seen that, when the scanning electron microscope image wassubjected to EPMA mapping, a part occupied by copper was displayed inFIG. 10A, and a part occupied by nickel was displayed in white color inFIG. 10B. Therefore, the area ratio of nickel to copper in the internalelectrode may be calculated from the images of copper and nickel. Thearea ratio data of Table 1 above were calculated in this manner.

According to exemplary embodiments of the present invention, thecopper-nickel mixture is used as a material for the internal electrodeof the multilayer coil component to form the nickel and ferrite mixedregion at the interface between the internal electrode and the ceramiclayer, thereby interrupting contact between the ceramic layer and theinternal electrode, so that insulation resistance, which may begenerated between the two materials can be increased and thus thedeterioration in the characteristics of the multilayer coil componentcan be prevented.

Further, according to the exemplary embodiments of the presentinvention, while the copper-nickel mixture is used as a material for theinternal electrode of the multilayer coil component, the nickel contentin the internal electrode is adjusted to thereby optimize the area ratioof nickel to copper, thereby preventing deterioration in characteristicsof the multilayer coil component, so that ferrite characteristics of themultilayer coil component, such as, impedance (Z), inductance (L), andthe like, can be improved.

Further, the internal electrode according to the present invention,formed of the copper-nickel mixture can be used in a general multilayerchip bead, a multilayer chip inductor, a multilayer power inductor, andthe like.

What is claimed is:
 1. A multilayer coil component comprising: a mainbody having a plurality of ceramic layers therein; and a plurality ofinternal electrodes formed on the plurality of ceramic layers,respectively, the internal electrodes being interlayer-connected to eachother through via holes of the ceramic layers to form a coil pattern,wherein the internal electrode contains a copper-nickel mixture.
 2. Themultilayer coil component according to claim 1, wherein thecopper-nickel mixture is at least one selected from the group consistingof a copper-nickel mixed powder, a copper-nickel alloy, and a copperpowder coated with nickel.
 3. The multilayer coil component according toclaim 1, wherein a nickel content in the internal electrode is 5˜25 wt%.
 4. The multilayer coil component according to claim 1, wherein theceramic layer is formed of NiZn ferrite or MnNiZn ferrite.
 5. Themultilayer coil component according to claim 1, wherein the multilayercoil component is a multilayer chip inductor, a multilayer chip bead, ora multilayer power inductor.
 6. A multilayer coil component comprising:a main body having a plurality of ceramic layers therein; and aplurality of internal electrodes formed on the plurality of ceramiclayers, respectively, the internal electrodes being interlayer-connectedto each other through via holes of the ceramic layers to form a coilpattern, wherein the internal electrode contains a copper-nickelmixture, and wherein a nickel content in the internal electrodesatisfies 5≦Ni(wt %)≦25.
 7. The multilayer coil component according toclaim 6, wherein the copper-nickel mixture is at least one selected fromthe group consisting of a copper-nickel mixed powder, a copper-nickelalloy, and a copper powder coated with nickel.
 8. The multilayer coilcomponent according to claim 6, wherein the ceramic layer is formed ofNiZn ferrite or MnNiZn ferrite.
 9. The multilayer coil componentaccording to claim 6, wherein the multilayer coil component is amultilayer chip inductor, a multilayer chip bead, or a multilayer powerinductor.
 10. A multilayer coil component comprising: a main body havinga plurality of ceramic layers therein; and a plurality of internalelectrodes formed on the plurality of ceramic layers, respectively, theinternal electrodes being interlayer-connected to each other through viaholes of the ceramic layers to form a coil pattern, wherein the internalelectrode contains a copper-nickel mixture, and wherein a nickel andferrite mixed region is formed at an interface between the internalelectrode and the ceramic layer.
 11. The multilayer coil componentaccording to claim 10, wherein the nickel and ferrite mixed region isformed by containing nickel of the internal electrode and ferrite of theceramic layer.
 12. The multilayer coil component according to claim 10,wherein the nickel and ferrite mixed region has a thickness of 0.2˜5 μm.13. The multilayer coil component according to claim 10, wherein anickel content in the internal electrode is 5˜25 wt %.
 14. Themultilayer coil component according to claim 10, wherein thecopper-nickel mixture is at least one selected from the group consistingof a copper-nickel mixed powder, a copper-nickel alloy, and a copperpowder coated with nickel.
 15. The multilayer coil component accordingto claim 10, wherein the ceramic layer is formed of NiZn ferrite orMnNiZn ferrite.
 16. The multilayer coil component according to claim 10,wherein the multilayer coil component is a multilayer chip inductor, amultilayer chip bead, or a multilayer power inductor.